Historically, one of the difficulties encountered when severing tubing has been that the severing knife deforms the tube by inwardly deflecting the tube wall at the location of severance. In order to minimize or avoid this dimpling or deformation, tube severing machines have been designed which first notch the tube along a shallow groove in the exterior of the tube wall in a direction transverse to the tube axis just prior to the entry of a severing blade. The severing blade severs the tube wall completely with one powerful downward stroke, the severing blade first contacting the tube in the notched portion of the tube wall. By notching the tube wall before severing the tube wall in a guillotine-type cutting operation, there is less tendency for the tube to be dimpled or disfigured at the location of severance. The notch formed by a notching apparatus in the plane of severance reduces or eliminates the tendency of the tube wall to collapse upon entry of the severing blade. One advantage of this "double-cut operation" involving notching before severing is that no further operations are needed to restore the tube end to a round configuration such as would be necessary if the severance caused deformation of the tube end.
Several patents disclose machines which perform this "double cut operation". Such machines typically comprise a notching apparatus and a severing apparatus. The notching apparatus is often interconnected with an upper platen of a die set by way of a mechanical cam and cam follower such that the descent of the upper platen toward the lower platen causes the notching blade holder to travel in a direction transverse to the tube axis. Both thrust and pull across motions are known. An example of a mechanism which utilizes both the pull across and thrust motions for the notching apparatus us U.S. Pat. No. 4,646,601 which is herein incorporated by reference in its entirety.
Attached to the upper platen of such machines is a severing blade which is fixedly secured to the upper platen and moves vertically downwardly in a swift stroke to sever the tube in the vertical plane in which the tube has been notched. U.S. Pat. Nos. 3,938,415; 4,109,555; 4,108,029; and 5,088,365 all disclose a tube severing apparatus which utilizes this double cut operation.
Various blade configurations have evolved, some of which include hook portions such as is disclosed in U.S. Pat. No. 4,993,298. Other notching blades such as the notching blade disclosed in U.S. Pat. No. 4,796,498 have two cutting points that are staggered one below the other so that as the notching blade comes across the tube, the higher notching point notches a shallow first cut in the tube wall and immediately thereafter a second deeper cutting point notches a deeper cut in the inner tube wall. Other notching blades have multiple cutting surfaces or points so that the same blade may be slightly rotated to present a new cutting area when the first cutting area becomes dull and ineffective. U.S. Pat. No. 4,646,601 discloses such a notching blade which is triangular in configuration and may be rotated 120.degree. in order to present a new cutting surface used to notch the tube prior to severance. Utilizing blades which have multiple cutting edges enables a user to simply loosen the notching blade apparatus and rotate the notching blade so as to expose a new cutting surface or edge rather than replacing a notching blade once it is worn and needs to be replaced. Therefore, a blade with multiple cutting edges which simply may be rotated in order to expose a sharp cutting edge may be used for more repetitions than blades with simply one cutting edge and, thus, reduces the number of blades required for a predetermined number of repetitions. Because the notching blade does not have to be replaced as often, substantial time may be saved increasing the time the machine can be operational, thus increasing production. Substantial time and cost savings are the result.
U.S. Pat. No. 4,646,601 discloses a notching blade having multiple cutting surfaces which is held in place by one screw which passes through the blade and into a recess in a notching blade holder. As the notching operation is repeated over and over again, the notching blade may tend to move slightly, thus adversely effecting the integrity of the notch to be cut in the tube. A notching blade which is not securely held in a fixed position on a notching arm may result in inaccurate non-uniform notches across tubes and the stress caused by the mis-alignment of the notching blade with the notching blade holder may eventually cause the notching blade to shear or break.
Therefore, it has been one objective of the present invention to provide a notching blade holder which is capable of securely fastening an indexable notching blade in the notching blade holder.
It has been a further objective of the present invention to provide an indexable notching blade configured so as to be securely fastenable in a notching blade holder in order to increase the life span of the notching blade.
It has been a further objective of the present invention to provide a uniquely shaped notching blade which is specifically adapted to be mounted in a notching blade holder and secured against movement by a plurality of pins extending outwardly from the notching blade holder.